[Paper Review] Spin-Chiral Bulk Fermi Surfaces of BiTeI Proven by Quantum Oscillations

Joonbum Park, Erik Kampert+11 more|arXiv (Cornell University)|Jun 7, 2013

Organic and Molecular Conductors Research1 references3 citations

TL;DR

This study uses de Haas-van Alphen and Shubnikov-de Haas quantum oscillation measurements to map the spin-chiral bulk Fermi surfaces of the non-centrosymmetric semiconductor BiTeI. It identifies a spindle-torus-type Fermi surface topology with oppositely circulating spin textures and reveals a giant effective g-factor of ~60, confirming strong Rashba and Zeeman coupling, establishing BiTeI as a platform for spin-polarized chiral states and exotic quantum phases.

ABSTRACT

We present the Fermi-surface map of the spin-chiral bulk states for the non-centrosymmetric semiconductor BiTeI using de Haas-van Alphen and Shubnikov-de Haas oscillations. We identify two distinct Fermi surfaces with a unique spindle-torus-type topology and the non-trivial Berry phases, confirming the spin chirality with oppositely circulating spin-texture. Near the quantum limit at high magnetic fields, we find a substantial Zeeman effect with an effective g-factor of ~ 60 for the Rashba-split Fermi surfaces. These findings provide clear evidence of strong Rashba and Zeeman coupling in the bulk states of BiTeI, suggesting that BiTeI is a good platform hosting the spin-polarized chiral states.

Motivation & Objective

• To unambiguously identify the topology and spin chirality of bulk Fermi surfaces in BiTeI, a non-centrosymmetric semiconductor with a giant Rashba effect.
• To resolve the long-standing ambiguity in distinguishing bulk versus surface states in previous ARPES studies by using bulk-sensitive quantum oscillation techniques.
• To quantify the strength of Rashba and Zeeman coupling in the bulk by measuring the effective g-factor and Berry phase.
• To establish BiTeI as a viable 3D platform for hosting spin-polarized chiral states and exotic electronic orders without spin degeneracy.

Proposed method

• Conducted de Haas-van Alphen (dHvA) torque magnetometry on single crystals to probe bulk Fermi surface topology and Berry phase.
• Performed Shubnikov-de Haas (SdH) resistivity measurements in high magnetic fields (up to 62 T) to cross-validate Fermi surface features and extract Landau level quantization parameters.
• Employed both static and pulsed magnetic fields across multiple crystal orientations to map Fermi surface anisotropy and extract angular dependence.
• Analyzed Landau level fan diagrams using the equation $ n = \frac{F}{B} - \gamma_{B\rightarrow 0} - C\left[\frac{d\gamma}{dB}\right]_{B\rightarrow 0} B $ to extract the zero-field Berry phase $ \gamma_{B\rightarrow 0} $ and effective g-factor.
• Used first-principles calculations (LDA/GGA, VASP) to support the electronic structure and validate the observed Fermi surface topology.
• Combined data from four single crystals across multiple high-field facilities (NHMFL, HLD, Bitter magnet) to ensure reproducibility and high-field resolution.

Experimental results

Research questions

• RQ1 What is the true topology of the bulk Fermi surfaces in BiTeI, and do they exhibit spin chirality?
• RQ2 Can quantum oscillations distinguish between bulk and surface states in BiTeI, overcoming limitations of ARPES?
• RQ3 What is the magnitude of the effective g-factor in the Rashba-split bulk Fermi surfaces, and what does it imply about Zeeman coupling?
• RQ4 How do the non-trivial Berry phases and spin textures in the Fermi surface relate to the observed spin chirality?
• RQ5 To what extent do the large Rashba and Zeeman couplings in BiTeI enable spin-polarized chiral states in the bulk?

Key findings

• The bulk Fermi surface of BiTeI exhibits a spindle-torus-type topology, confirmed by angular dependence of quantum oscillations across multiple magnetic field orientations.
• Two distinct Fermi surfaces were identified with non-trivial Berry phases: $ \gamma_{B\rightarrow 0} = 0.3(2) $ for the inner surface and $ -0.35(9) $ for the outer surface, indicating oppositely circulating spin textures.
• The effective g-factor was measured to be ~56 for the inner Fermi surface and ~63 for the outer, yielding an average of ~60, significantly larger than the typical value of ~2.
• The strong nonlinear dependence of the Landau fan diagram at high fields confirms a substantial Zeeman splitting, with Zeeman energy comparable to the Fermi energy at ~10 T.
• The large g-factor and giant Rashba splitting (E_R ~ 150 meV) exceed the Fermi energy (~30 meV), indicating that spin-polarized chiral states are realized in the bulk under moderate magnetic fields.
• These findings establish BiTeI as a promising 3D platform for hosting spin-polarized chiral states and exploring exotic quantum phases such as FFLO superconductivity or Majorana fermions.